Synchronizing means are known from Looman-Zahnradgetriebe (Konstruktionsbucherband 26) Springer-Verlag Berling/Heidelberg/New York 1970, page 259FIG. 10.9, where the clutching tooth array of the sliding sleeve is locked onto the locking tooth array of the synchronizing ring as long as synchronism is not achieved between the synchronizing body and the gear. Such arrangements are very advantageous for the driver, because they require relatively little attention to shifting. However, they have the disadvantage that the friction means are overloaded due to the appearance of large differences in speed fo rotation and the high shifting forces frequently applied, and therefore wear out rapidly and fail prematurely. Particularly when shifting into reverse while the vehicle still moves ahead, relatively high differential speeds of rotation have to be synchronized, so that the synchronizing means are especially endangered for such a shift. However, the engine is also in jeopardy since in a locking synchronizing arrangement, the engagement of the reverse gear cannot be excluded with certainty during excessively fast forward motion. Upon clutching-in, the engine can be damaged because of reversal of rotation.